JP2023505417A - Container closure seals and container closures - Google Patents

Abstract

The present invention is a container closure seal, in particular for fat-containing fillings, comprising a polymer compound and consisting essentially or entirely of said polymer compound, wherein a) said polymer compound is PVC-free, at least one TPS and at least two different co-PPs or at least one co-PP having a Shore A hardness of up to 80, a crystallization enthalpy of up to 30 J/g and a melting point of at least 155°C and b) said polymer compound has a Shore A hardness of 30-85 at 70°C and a melt flow index (5kg/190°C) of less than 20g/10min. [Selection figure] None

Description

The present invention relates to PVC-free container closure seals, in particular for fat-containing filling materials, which contain polymeric compounds and consist substantially or entirely of polymeric compounds.

A major problem with polymer-based container closure seals is the migration of seal components into the filler. Migration problems are particularly frequent with grease- or oil-containing fillers, as migrating substances such as plasticizers and thinners are often fat-soluble.

Large container closures of the type contemplated herein are, in particular, lug cap closures typically used to close glass bottles with screw caps for food or beverages. These foods are often fat-containing products such as sauces, delicatessens, pickled fish, antipasto, spice pastes, etc., the fat or oil content of which is determined by the solubility of the fat-soluble components of the packaging material in the food. increase the risk of

These requirements are also particularly relevant to baby food products that are typically sold in bottles with press-on twist-off closures (referred to herein as PT closures or PT caps). .

The container closures affected here usually have an opening width of at least 28 mm, in particular at least 35 mm, such as 38 mm or more, such as 82 mm or more. A lug cap closure can have four, five, or more than five lugs.

Conventional PVC-based container closures exhibit good sealing properties. Based on flexible PVC technology, it is also possible to formulate low-migration sealants, which often use polyadipates. Polyadipate is difficult to migrate due to its molecular weight.

The routine analytical method EN 1186 for evaluation of migration assumes complete migration after storage at 40°C for 10 days. Analytical conduct shows that this is not the case with softened PVC, so that the closure exceeds the transition limit after only a few months, even though the test conditions are met.

The use of PVC-containing compounds in packaging is also undesirable. In the combustion of ordinary household waste, halogenated plastics produce acid gases that are harmful to release into the atmosphere. Also, even a small amount of PVC inhibits material recycling of plastic waste. Also, such PVC-based sealing elements require the use of plasticizers, which are also questionable due to undue alteration of food products. Also, in recent years there has been public debate about the additives and their decomposition products used in PVC seals. Examples include 2-ethylhexanoic acid, often derived from stabilizers, and semicarbazide produced from exothermic blowing agents such as azodicarbonamide. These substances have also been found in fillers during official control and their presence has been challenged.

Migration of packaging components (which may also include sealing inserts of container closures, if applicable) into food is not only generally undesirable, but is also strictly regulated by legal provisions. Examples of such provisions are Supplement (EU) 321/2011, (EU) 1282/2011, (EU) 1183/2012, (EU) 202/2014, (EU) 174/2015, (EU) 2016/ 1416, EC Regulation 1935/2004, including (EU) 2017/752, (EU) 2018/79, (EU) 2018/213, (EU) 2018/831, (EU) 2019/37 and (EU) 2019/1338 , 2023/2006, (EU) 10/2011 and the like. Currently, a maximum level of 60 ppm of migrating ingredients is allowed in infant foods.

If applicable, the determination of the degree of migration observed is carried out in particular by the method defined in DIN EN1186. Such methods are also used in the context of the present invention.

Therefore, there is a need for a PVC-free container closure seal that comes as close as possible to the desirable properties of known PVC-containing seals.

According to the invention, PVC-free compounds are used. In products according to the present invention, migration can be largely or completely avoided by avoidance of liquid ingredients and/or use of poorly migrating polymers and other means.

For container closures of the type considered here, the provision of PVC-free sealing inserts would be trivial if these closures were to comply with the above stipulations regarding the potential for migration of their chemical constituents. Not a trivial problem. The sealing function must also be guaranteed under filling conditions.

The demands on the sealing material for container closures with a larger inner diameter of the container opening (at least 28 mm, often at least 35 mm) are more stringent due to the relatively large amount of material in the seal. For such purposes, it is of particular importance to combine sufficient fluidity of the polymer material in the manufacture of the sealing element with sufficient sealing properties in the sealed state, which includes gas penetration. It also includes the currently required tightness against leaks (escape), combined with the effect of pressure relief valves where applicable, explosion of the container during heating or for other reasons. overpressure can be prevented. It is also noted that in typical applications, especially for containers with larger opening diameters (e.g. canned food), the sealing element can also be used under pasteurized conditions (at least 98°C) and optionally sterile conditions (100°C to 132°C). requested.

A seal with all these properties must also fulfill the above requirements with respect to possible migration of chemical constituents.

Container closures need to attach to containers to be sealed quickly and with minimal evaporation. It should also be suitable for manual closure in addition to normal mechanical sealing processes.

A solution to these problems has been successfully introduced in the meantime and is disclosed in our patent application EP09756681, now patent EP2470435. The seals described herein are PVC-free and contain at least one olefin block copolymer (OBC) and at least one polyolefin elastomer (POE), high density polyethylene (HDPE) or polypropylene or propylene copolymer ((co-) PP). and should not contain TPS. The Shore A hardness is 45-95 and the compression set is 30%-90%.

A similar container closure is known from WO2012/152329, the seal comprising a polymer compound with 35% homo-PP, 44% OBC/TPS and 20% POE.

To facilitate processing of conventional compounds, thinners and/or plasticizers are usually added to them. In particular liquid components such as foamed oils and/or plasticizers (preferably white oils) are used at the application temperature. However, lubricants and liquid components at 20°C are substantially or preferably completely eliminated in the known formulations, as they may accelerate migration.

The product known from EP09756681 is ideal for many uses, but can be improved for some uses. For example, in mechanical sealing processes, if the closing distance is very short and the machine can only adjust over a limited range, it can lead to sever seals. In the case of very fast running machines for pre-evaporated closures, the processing time may not be sufficient for adequate warm-up of the closures.

It is therefore desirable to have a seal that is thermally stable and softer than the seal known from EP09756681, leading to fewer cuts occurring. This seal should preferably have the advantageous properties of known seals.

The seal should also have the lowest possible opening values so that screw closures such as cam screw closures, PT closures or other screw closures can be easily opened. The opening cannot be too low, as it must be ensured that the closure cannot open unintentionally.

With conventional 82mm Twist-Off® closures, PVC-containing seal openings are often 42-55 inches/pound (lbs) or more. A technically complex Orbit® closure with a low migration value PVC-based seal designed to reduce the torque required to open is less than 4 Nm. Typical openings for Twist-Off® closures with known seals according to EP09756681 are 4.3-5.1 Nm. A lower opening is advantageous for PVC-free closures.

The manufacture of seals having the above properties is an essential object of the present invention.

The invention solves these and other problems in principle by means of the combination of features specified in the independent claims.

Similar to the solution according to EP 0 975 6 681, which is fully incorporated in the disclosure of the present application by reference, the seal of the present invention is preferably introduced into the metal or plastic closure blank in a thermally sufficiently flowable form. This includes a polymeric compound that is stamped or the like into a desired shape and retained after cooling. In these cases the finished seal is usually composed entirely of polymeric compounds. Corresponding manufacturing process machines are available, for example, from SACMI.

The terms "seal", "seal insert" and "seal element" are synonymous in the context of this specification.

Also in the case of the container closure according to the invention the sealing element is formed as an insert in the inner surface of the container closure, as in the case of known crown caps or screw closures.

In principle, the manufacturing method according to the invention preferably envisages metal container closure blanks which are first pretreated on the inside with a suitable primer. In the case of container closures made of plastic, this pretreatment is not necessary.

Typically, the coating system of the primer consists of a basecoat and an adhesive varnish, both of which can be based on epoxy-phenolic resin systems or (usually for regulatory reasons) on polyesters. In particular, the coating systems of ACTEGA Lenania (base paint TPE279 with adhesive varnish TPE1500 or ACTEcoat® TPE515 with ACTEbond® TPE-655-MF) contain the most preferred compounds according to the invention. Adheres particularly well.

Alternatively, a suitable primer coating can also be applied by lamination or optionally co-extrusion.

In a preferred embodiment, the pretreated blank is internally applied with a polymeric material in a thermally flowable form to form a seal. Extrusion is particularly suitable for this, in which case the sealing compound is presented in the temperature range from 100°C to 260°C.

Extrusion can be done approximately in the middle of the inner surface of the blank if the seal insert is disc-shaped. Dosing of polymeric material for extrusion is accomplished by exfoliating a defined amount of polymeric compound from the nozzle.

In the case of known bottle closures (such as crown caps), the sealing element is usually formed as a disc inside the container closure, but in the case of the large container closure according to the invention, instead, the closure of the container It is preferred to form only a ring of polymeric material which underlies the container wall in the open area.

For this purpose the method described in US 5,763,004, which is incorporated herein by reference, can be used.

A disk-shaped sealing element is then preferably formed from the still flowable extruded material by suitable stamping (similar to the well-known SACMI method).

Alternatively, the sealing element can be formed on the outside of the closure or closure blank by stamping a suitable polymeric material and then inserted into the closure or blank. This method is also known in SACMI as shell-molding.

As a main or single component, the material of the seal insert is in one variant composed of at least three different polymers, i.e. at least one TPS and a first co-PP and at least in physical and/or chemical parameters It includes a PVC-free polymer component (ie, polymer compound) that includes a first co-PP and a different second co-PP. In a second variant, the components comprise at least one TPS and at least one co-PP, wherein the co-PP has a Shore A hardness of up to 80 and an enthalpy of crystallization of up to 30 J/ g and the MFI is less than 20 g/10 min.

The properties of this main polymer component can be suitably modified by adding further components, eg further polymers.

Thus, the present invention separates itself from the concept known from EP09756681 that the desired seal or polymeric compound of the seal must contain an OBC. An OBC may, but does not have to, be included in a seal according to the invention.

Furthermore, the present invention separates itself from the concept according to EP09756681 that the seal or seal compound may not contain TPS.

Instead, the present invention provides that when the polymer compound comprises certain types of TPS, especially SEBS in combination with certain types of co-PP, thermally and mechanically stable, but softer, general purpose seals can be obtained. It is based on the knowledge that it can be obtained. As explained below, not all known types of TPS and all known types of co-PP are suitable for this.

Preferably, the material of the sealing insert has a very low content of components that are liquid at the application temperature, particularly preferably no content. The application temperature is usually equal to the ambient temperature, ie within the range of normal ambient temperatures outdoors or in a heated room. Typically the application temperature is 20°C.

Therefore, preferably no liquid thinner, especially white oil, is added to the material of the seal insert in small amounts or preferably not at all.

Preferably, the material contains no more than 10%, preferably no more than 7%, especially no more than 5% of a lubricant, the lubricant having a limited manner in a migration test of 10 days at 40°C. ) through a fat-containing filler (percentages in this application are always weight percentages based on the total weight of the compound in the seal unless otherwise stated).

The material contains no liquid components at 20° C. and does not contain conventional plasticizers, within the analytical limits of determination given in the prior art at the time of application. is currently most preferred.

The polymeric compounds of the present invention generally have a Shore A hardness of 30-85, more specifically 40-75, at 70°C. The lower the hardness, the easier it is to install the closure. When used in steam vacuum capping machines, there is a high risk of cutting when the hardness is below 30 Shore A. If the hardness is Shore A85 or higher, the risk of failure in sealing increases. When used in a cold vacuum sealing machine without preheating, a Shore A hardness of 85 or greater will not create a vacuum.

The polymer compound preferably has a high viscosity, i.e. an MFI according to DIN EN ISO 1133 (5 kg/190° C.) of less than 20 g/10 min, more preferably less than 15 g/10 min, more preferably less than 10 g/10 min, Especially preferred is less than 6 g/10 minutes. Other viscosity settings are useful, especially when processing in a cold vacuum sealing machine.

The compression set of the polymer compound according to DIN ISO 815-1, type B, method A, isotropic specimens is
5% to 45%, especially 10% to 40%, preferably 15% to 30% at 4°C;
15% to 55%, especially 20% to 50%, preferably 25% to 40% at 23°C;
At 70° C., it is 35% to 85%, especially 50% to 80%, preferably 55% to 70%.

A useful method for characterizing the mechanical properties of elastic polymeric materials is the anisothermal stress relaxation test (AISR method). According to VENNEMANN (e.g. essay "PRAXISGERECHTE PRUFUNG VON TPE" (translation for understanding the subject: "Practical Oriented Testing of TPEs")), the heat application limits of TPEs can be determined in this way. . As an essential parameter, the limit temperature is determined by a test in which 90% of the initially applied stress is reduced by 50% when the S2 specimen is stretched at room temperature (T90). The higher the determined limit temperature T90, the higher the thermal stability of the material under test.

The "TSSR meter" from Brabender Messtechnik is suitable for carrying out this measurement method. This method serves as an alternative or supplement to the known (and standardized) determination of compression set and provides data correlating with the elasticity of polymeric materials.

The T90 value indicates from which temperature the voltage is reduced by 90%, ie at a particular temperature the sealant or compound has only 10% voltage. Experience shows that all compounds according to the invention have T90 values of at least 80°C. The T90 value reads whether there is a low hardness of less than 40 Shore A hardness at 70°C or no cuts during the sealing process by a steam vacuum sealing machine with a TSSR initial force of 10 N at 80°C and T90. be able to.

Also, the force required to generate 50% voltage at 23° C. can be read. Surprisingly, the inventors found that the risk of cutting (steam-vacuum capping machine) is high at forces less than 10N, and at forces greater than 40N, commercial steam and cooling vacuum In both steam as well as cold vacuum sealing machines, we have found that sealing is often problematic. These are mainly manifested by the vacuum loss immediately after the sealing process, leading to rejections during manufacturing.

This problem applies to all steam vacuum capping machines and cooling vacuum sealing machines commonly used at the date of registration, e.g. The same is true for crown global cappers.

The preferred range of force for the polymer compound according to the invention is 15N-25N (strain 50%/23°C) for vapor vacuum sealing machines and 5N-15N for cooling vacuum sealing machines.

After sealing, during and after the cooling process, and also during storage in sealed containers, PVC-free compounds often lead to a crystallization process of the polymeric compound. These affect the stiffness and elasticity of the seal and thus the tension between the closure and the container upon cooling after the sealing process. The slower the crystallization, the smaller the buildup voltage, which adversely affects the opening torque.

The peak crystallization temperature and the total weight-related crystallization enthalpy are determined by DSC measurements (dynamic scanning calorimetry) from the first cooling curve. The rules are described in the ISO 11357 standard or its subchapter (especially 15011357-3). Quantities were measured using a Mettler Toledo DSC1 system.

An example of a DSC curve is shown.

In describing the suitability of seals for vacuum screw closures, it has been found useful to design the polymer compound so that the temperature of the exothermic peak is higher than the maximum expected use temperature of the container closure. The exothermic peak temperature from the crystallization process is well below the temperature of the partially endothermic melting peak.

Basically, the present invention prefers to use such polymers with low crystallinity, in particular crystalline polymers such as homoPP, LLDPE, LDPE and HDPE are preferably not used or reduced. used only to an extent.

Preferred polymeric compounds have a specific total enthalpy of crystallization of less than 45 J/g, more preferably up to 38 J/g, more preferably up to 30 J/g at room temperature or above.

The TPS used in the present invention is preferably SEBS and/or SEEPS. Additionally or alternatively, at least one polybutene can be used.

Generally, linear SEBS and/or SEEPS with styrene content levels of 26% to 34% are preferred. Particularly preferred are SEBS and/or SEEPS with a styrene content level of 29% to 33%, and generally preferred are SEBS and/or SEEPS with a styrene content of 31% to 32%.

Preferred polymeric compounds generally contain up to 50%, more specifically up to 45%, more preferably up to 40% TPS. Preferably, such polymeric compounds comprise at least 10%, particularly at least 20%, more preferably at least 30% TPS.

TPS by itself is not a particularly suitable polymer for sealing compounds in contact with fatty or oily fillers, as it promotes the penetration of grease and oil into the seal. This is especially true for products that have been heat treated, such as pasteurized or sterilized.

According to EP 09756681 the TPS content in the polymer compound should be eliminated as much as possible.

Surprisingly, however, it has been found that TPS can also be successfully used in sealing compounds for grease and oil applications when the polymer compound comprises a specific polypropylene copolymer (co-PP). Clearly, the inclusion of co-PP prevents the absorption of fats and oils through the seal even in the presence of TPS, and pasteurization, even sterilization (at temperatures up to 132°C), homo-PP prevents the absorption of co-PP. Instead, it is not used in the preferred embodiment of the invention.

In a preferred embodiment of the invention, the TPS portion of the polymeric compound is composed of at least two different TPS, especially two different SEBS.

The main component of this TPS content has a Shore A hardness of 50-90, preferably 55-80, and a dynamic viscosity of >50 mPa·s (measured at 25° C.) as a 5 wt % solution in toluene. ) and, as a 10% by weight solution in toluene, linear SEBS with a dynamic viscosity >1000 mPa·s is preferably used.

A particularly preferred SEBS in this proportion is a linear triblock copolymer of type SE/BS.

Products such as Kraton® G1651 and Carprene® 6174 are particularly suitable.

In addition, as a modifier, the styrene content is 10% to 23%, the Shore A hardness is 30 to 60, and the MFI (2.16 kg/230°C) is 2 to 30 g/10 minutes. of SEBS is preferably used.

The use of Kraton® G1645 or G1643 mixed with Kraton® G1651 can increase the flexibility of the compound (in the sense of plasticizer instead of white oil).

The polymeric compound further has a content of at least one co-PP.

The present invention preferably uses the content of one or more co-PPs instead of the content of homo-PPs in the polymer compound.

In a first variant of the invention, the polymer compound comprises two different co-PPs.

The first co-PP preferably has a Shore D hardness of 25 or less, more preferably 20 or less.

The first co-PP preferably has a DSC melting point of 145° C. or higher, more preferably 155° C. or higher. The melting point of the first co-PP is preferably higher than the melting point of the second co-PP.

The first co-PP preferably has a total enthalpy of crystallization that is less than 30 J/g, more preferably less than 25 J/g, usually preferably less than 20 J/g.

The MFI (2.16 g/10 min) of the first co-PP is preferably 30 or less, more preferably 20 or less, and usually preferably 10 g/10 min or less.

The second co-PP preferably has a Shore D hardness of 25 or greater, more preferably 30 or greater, but 45 or less.

The second co-PP preferably has a DSC melting point of 140° C. or higher, more preferably 145° C. or higher.

The second co-PP preferably has a total enthalpy of crystallization of less than 40 J/g, more preferably less than 35 J/g.

The MFI (2.16 g/10 min) of the second co-PP is preferably 35 or less, more preferably 25 or less, and usually preferably 10 g/10 min or less.

The total amount of co-PP used in the compound is preferably preferably between 20% and 65%. The content level of the first co-PP is preferably higher than the content level of the second co-PP.

Particularly preferred products are Adflex grades C290F and Q190F from Lyondell-Bessel, Ducria QT80A from Ducor and Tafmer PN3560 from Mitsui Chemicals.

In preferred embodiments of the invention, the co-PP may be partially replaced by other polymers such as LLDPE.

In a second variant of the invention, the polymer compound contains at least one co-PP with a Shore A hardness of at most 80, an enthalpy of crystallization of at most 30 J/g and a melting point of at least 155°C. .

Also, in a second variant, the polymeric material may contain other polymers, such as other co-PPs or polyolefins.

As a further component of the polymeric compound, the present invention uses, in certain embodiments, the content of at least one POE.

A preferred POE contains PP units and randomly copolymerized ethylene units.

The POE content is preferably 10% to 50%, more preferably 20% to 40%. Vistamax grades from ExxonMobil, such as Vistamax 6202, are particularly suitable.

The polymeric material can withstand hot fills up to 100° C. for up to 60 minutes starting with hot fills of at least 60° C. for up to 10 minutes and at least 1 minute. Hot filling starting at 60° C. can be stepped from 5° C. up to 100° C. in 60 minutes.

Optionally, it is also possible to add pigments, preferably inorganic pigments, to the compound formulation to eliminate pigment migration. It is also indicated that other additives such as waxes, silicones, and especially blowing agents can be added to the polymeric compounds, for example to improve processing and performance properties.

In the following, exemplary embodiments of the present invention are described based on the composition of the polymeric compound from which the container closure seal according to the present invention is formed as described above.

[Exemplary embodiment 1]
15% first co-PP
14% second co-PP
33.4% SEBS 35% POE
2.6% lubricants and additives

[Exemplary embodiment 2]
20% first co-PP
14% second co-PP
33.4% SEBS
30% POE
2.6% lubricants and additives

Claims (21)

A container closure seal, especially for fat-containing fillings, comprising a polymeric compound, said container closure seal consisting essentially or entirely of:
a) said polymeric compound is PVC-free, comprises at least one TPS and comprises at least two different co-PPs or has a Shore A hardness of up to 80 and an enthalpy of crystallization of up to 30 J/g; , comprising at least one co-PP having a melting point of at least 155° C.;
b) the polymeric ethanol has a Shore A hardness of 30-86 at 70°C, a melt flow index (5 kg/190°C) of less than 20 g/10 min, and does not contain more than 10% liquid component at 20°C; Container closure seal. 2. The at least one co-PP according to claim 1, wherein the at least one co-PP has a Shore A hardness of up to 75 and/or a crystallization enthalpy of up to 20 J/g and/or a melting point of at least 160°C. container closure seal. 3. A container closure seal according to claim 1 or 2, wherein said polymeric compound is substantially free of homo-PP. A container closure seal according to any preceding claim, wherein the polymeric compound comprises at least one of SEBS, SEEPS or polybutene. Claim wherein said polymeric compound comprises linear SEBS or SEEPS having a styrene content level of 26% to 34%, specifically 29% to 33%, most preferably 31% to 32% styrene. A container closure seal according to any one of claims 1-4. A container closure seal according to any one of the preceding claims, wherein said polymeric compound comprises at least 20%, more preferably at least 30% TPS. Said polymeric compound has a Shore A hardness of 50 to 90, preferably 55 to 80, a dynamic viscosity of >50 mPa·s (measured at 25° C.) as a 5% by weight solution in toluene, A container closure seal according to any one of the preceding claims, containing linear SEBS with a dynamic viscosity >1000 mPa·s as a 10% by weight solution therein. a second SEBS, wherein the polymer compound has a styrene content of 10% to 23%, a Shore A hardness of 30 to 60, and an MFI (2.16 kg/230° C.) of 2 to 30 g/10 min; A container closure seal according to any one of claims 1 to 7, comprising. The polymer compound comprises a first co-PP having a Shore D hardness of 25 or less, more preferably 20 or less, and a second co-PP having a Shore D hardness of 25 or more, more preferably 30 or more but 45 or less. A container closure seal according to any one of claims 1 to 8, comprising a co-PP of The polymer compound comprises a first co-PP having an MFI (2.16 g/10 min) of 30 or less, more preferably 20 or less, most preferably 10 g/10 min or less; 10 min) is 35 or less, more preferably 25 or less, most preferably 10 g/10 min or less and a second co-PP. . The polymer compound comprises at least one co with an MFI (2.16 kg/230° C.) of at least 0.1, more specifically at least 0.3, even more specifically at least 0.5 g/10 min. - A container closure seal according to any one of the preceding claims, comprising PP. A container closure seal according to any preceding claim, wherein the DSC melting point of the first co-PP is higher than the DSC melting point of the second co-PP. A container closure seal according to any one of the preceding claims, wherein said polymeric compound comprises a first co-PP having a DSC melting point of 145°C or higher, more preferably 155°C or higher. A container closure seal according to any one of the preceding claims, wherein said polymeric compound comprises 20% to 70% co-PP. Container closure seal according to any one of the preceding claims, wherein said polymer compound comprises at least one POE, preferably PP based copolymer. A container closure seal according to claim 15, wherein the POE content is between 10% and 50%, more preferably between 20% and 40%. Claims 1 to 16, wherein the polymeric compound contains no more than 10%, preferably no more than 7%, in particular no more than 4%, particularly preferably no more than 2.5% lubricant A container closure seal according to any one of Claims 1 to 3. 18. The polymer compound according to any one of the preceding claims, wherein the polymeric compound contains, at 20° C., not more than 7%, in particular not more than 4%, particularly preferably not more than 1% liquid component. container closure seal. Container closure seal according to any one of the preceding claims, which is pasteurizable at a temperature of 98°C or above, preferably sterilizable at a temperature of 100°C or above up to 132°C. A metal or plastic container closure, in particular a vacuum container closure, comprising a container closure seal according to any one of claims 1-18. 21. Container closure according to claim 20, having a diameter of at least 28 mm, preferably at least 35 mm.

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